Respiratory Health and Cross-Shift Changes of Foundry Workers in Iran

Background: Respirable dust exposure is associated with increased respiratory impairment. As there are various airborne contaminants in the foundry industry, our aim was to thoroughly examine the acute effects of ambient respiratory dust on the respiratory system. Materials and Methods: A cross-shift study was conducted in a cast iron foundry in Iran. A total of 200 participants, including 110 workers from production department and 90 office workers were enrolled in this study. Workers were evaluated with regard to respiratory symptoms using the American Thoracic Society (ATS) questionnaire and examination of their lung function by spirometry. Results: The mean exposure of all studied substances was higher than occupational exposure limits. The most common respiratory symptom in exposed workers was cough (24.5%). A statistically significant post shift reduction in FEV1 and FEF25-75 was seen in exposed group. After adjusting for age, working history, smoking and Body Mass Index (BMI), there was a significant decrease based on exposure in FEV1 and FVC. Conclusion: Dust exposure was a significant predictor of lung function. Implementing the health promotion program, periodic medical surveillance and efficient use of respiratory protection equipment could help to protect foundry workers from respiratory impairment.


INTRODUCTION
It is well established that exposure to airborne contaminants in occupational industries increases the risk of developing respiratory diseases. Respiratory problems due to occupational exposures are influenced by the particle type, size, concentration, exposure duration and individual susceptibility. In addition to these factors, exposure to respiratory hazards varies according to the type of industry and also climate condition (1,2).
The foundry produces metal castings through the process of pouring the metal in a mold, and removing the cast after the metal has solidified. There are several working stations in the foundry that include: melting, furnace, mold making, casting, cleaning and finishing (3).
Foundry workers are at risk of respiratory problems due to exposure to metal fumes, iron oxide, polycyclic aromatic hydrocarbons, gases, resins, isocyanates and dusts such as crystalline silica (4). These workers are at increased risk of respiratory impairment due to different exposures. Several studies have shown the association between foundry production and chronic effects on respiratory system, including chronic obstructive airway disease, pneumoconiosis, and cancers (5)(6)(7)(8)(9)(10), but to the best One of the most important diagnostic methods for early detection of pulmonary dysfunction is spirometry (11).
This study was designed to assess the acute effect of occupational exposures to respiratory hazards on the lung function of foundry workers. The effects of chronic exposure to airborne pollutants and associated factors on the lung function have also been examined.

MATERIALS AND METHODS
This cross sectional study was carried out in Tehran, one of the provinces of Iran. This 40-year factory is one of the most important and experienced cast iron foundries in the eastern region of Tehran, which has been in continuous production of a wide range of standard cast iron grades, including: white, gray and ductile. Two hundred subjects were enrolled in our study using random sampling based on the following criteria: male, age from 20-65 years old and at least 2 years work experience. One hundred and ten workers in the production process and 90 office workers were selected as exposed and non-exposed groups, respectively. Data were analyzed by SPSS 22 (Chicago, IL, USA). Chi square test was used for determination of association between two qualitative variables, while independent sample t-test was used to evaluate the difference between quantitative variables both in exposed and non-exposed

RESULTS
A total of 110 cast iron foundry workers as an exposed group were examined in the study along with 90 office workers as non-exposed group. Time Weighted Average The mean age was 39.1±8.9 ranging from 20-65 years.
The exposed groups were significantly older and had lower education. The exposed population was found to have smoked more than the office workers (OR: 2.34). The difference in the mean Body Mass Index (BMI) and working history between two groups did not differ significantly (Table 2).
It was shown that cough was the most frequent symptom in the exposed group (24.5%). Fifty-five (55.6%) of exposed group who had respiratory complaints were used to wearing masks in comparison with 44 (44.4%) who had no protection (p value 0.094). The lung function values for FVC and FEV1 were significantly lower for the exposed group (

DISCUSSION
The workers at the cast iron foundries are exposed to dust, fumes, and solvents comprising silica, carbon, iron oxide, lead oxide, manganese, toluene and benzene (6).

Most of these airborne contaminants have been shown to
have an adverse effect on the pulmonary function of exposed workers (15). In our study, cast iron foundry workers were found to have been exposed to higher concentrations of respirable dust than non-exposed group; furthermore, the measured respirable dust was higher in the sand casting section. On the other hand, office workers as the non-exposed group did not have any exposure to airborne contaminants, although 58.2% of exposed group normally wear protective masks. The workers who normally wear protective masks have lower frequency of respiratory symptoms (16). We found no association between wearing masks and respiratory complaints. It may be due to inappropriate mask type (simple instead of filtering-face piece respirators), insufficient and irregular use of the protection. According to the survey findings, there are potentially inadequate respiratory protection programs in metal industries (17). It is the obligation of each organization to evaluate its own respiratory protection program with respect to the Occupational Safety and Health Administration (OSHA) standards (18).
Therefore, regular use of high quality personal protective equipment is recommended.
A reduction in the FEV1 and FVC was observed in the exposed group, indicating that occupational exposure to respirable dusts in the cast iron foundry workers has an important role in decreasing lung function. Our findings were in line with previous studies. Low reported lower mean values of FVC among steel foundry workers (19).
Johnson found a significant decrease in FEV1 among iron and steel foundry workers (9). Similar effects have been found among 55 foundry workers and there was an inverse relation to dust exposure in a foundry plant and FVC (20).
We found that exposed workers have a higher frequency of respiratory symptoms including cough. Other studies in foundry workers showed similar results with an excess frequency of chronic bronchitis in exposed subjects (21,22).
In the present study, we found a cross-shift reduction in FEV1and FEF25-75 among the exposed group. Our

Limitations
Our study was done on currently employed workers, therefore the healthy workers' effect could have affected the results, when perhaps workers who had developed respiratory complaints were transferred or left the industry. Therefore, a follow up study or a comparative study of retired/resigned workers could reduce the healthy worker effect and better explain the association.
Moreover, this cross sectional study was conducted in one factory, so the generalizability and causal association of our results is limited. Also due to insufficient sample size, we couldn't compare different parts of the foundry processes.